I got that message before. Was pretty weird. Happened just after trying to turn my steering wheel in a parking lot, encountering no power assist, and then the warning message.
I've had other weird electronics issues over the past couple of months. Over the past weekend, I was performing a battery/electrical system test with my scan tool. I discovered the negative battery terminal loose. I had the car in for body work in November/December and know the body shop had disconnected the negative battery cable. I've tightened down the cable and so far no issues.
So I would check that or any engine grounds to see if they're loose or have rust/corrosion on them.